1. Technical Field
Embodiments of the present invention relate generally to an apparatus and method for compensating for duty signals and, more particularly, to a method of increasing the timing accuracy of a 25% duty signal required in the transmission stage or frequency synthesizer of a wireless communication system and to an apparatus and method for compensating for the timing error between an I signal and a Q signal.
2. Description of the Related Art
A Gilbert cell mixer used in a common wireless communication transmission stage and a frequency synthesizer requires a high power supply voltage in order to ensure sufficient linearity, and has poor timing characteristics attributable to a mismatch in a voltage current conversion circuit. Accordingly, the Gilbert cell mixer requires a technical change into a passive mixer. However, a passive mixer is problematic in terms of the degree of IF-RF separation, and requires the generation of a 25% duty signal within a local signal due to a crosstalk problem. The 25% duty signal has a very strong possibility that a timing mismatch may occur between an I signal and a Q signal.
Korean Patent Application Publication No. 10-2010-0050283 entitled “Receiver Capable of Compensating for Mismatch between I-signal and Q-signal and communication system thereof” (hereinafter referred to as conventional technology 1) relates to a receiver capable of compensating for a mismatch between an I signal and a Q signal and a communication system including the same. The receiver includes a frequency conversion unit configured to generate the in-phase signal and orthogonal phase signal of a multi-band frequency signal based on the multi-band frequency signal, and a mismatch compensation unit configured to estimate a mismatch between the in-phase signal and the orthogonal phase signal, appearing differently in each band of the multi-band frequency signal, with respect to each band, and to store at least one compensation value adapted to compensate for the estimated mismatch. The frequency conversion unit compensates for a mismatch between the in-phase signal and the orthogonal phase signal based on the at least one compensation value.
However, in conventional technology 1, a mismatch between the I and Q signals is estimated with respect to each band, at least one compensation value is required to compensate for the estimated mismatch, and only a mismatch between the phase differences of the I and Q signals is compensated for.